A large number of devices and methods are known for determining a presence and/or concentration of one or more analytes in body fluids. Without restricting the scope of this disclosure, in the following, reference is made mainly to determining glucose concentrations, particularly in body fluids such as whole blood and/or interstitial fluid. However, other applications and analytes are feasible.
For performing fast and simple measurements, several types of test elements are known, which use one or more test chemicals. The test chemical (also referred to as the test substance, the test chemistry, the test reagent or the detector substance) typically is a chemical compound or a mixture of chemical compounds adapted for performing a detection reaction for an analyte of interest. For details of potential test chemicals and test elements incorporating such test chemicals, which may be used herein, reference may be made to Hones et al. (2008) Diabetes Technol. Ther. 10:S10-S26. Other types of test elements and/or test substances are feasible and may be used herein.
By using one or more test chemicals, a detection reaction may be initiated, the course of which depends on the concentration of the analyte of interest. Typically, as may also be the case in, the test chemical is adapted to perform at least one detection reaction when the analyte is present in the body fluid, where the extent and/or the degree of the detection reaction depends on the analyte concentration. Generally, the test chemical may be adapted to perform a detection reaction in the presence of the analyte, where at least one detectable property of at least one of the body fluid and the test chemical is changed due to the detection reaction. The at least one detectable property generally may be a physical property or a chemical property.
In the following, reference will be made to optical detection reactions (i.e., optical test chemicals being adapted to change at least one optically measurable property in the presence of the analyte). The at least one optically detectable property generally may be detected by detecting light propagating from the test chemical to a detector. This light, which may be referred to as the detection light, may be light emitted by the test chemical itself and/or may be light that is scattered and/or reflected by the test chemical. Thus, the light may be luminescence light, such as fluorescence light, the generation of which may be excited by primary light, such as excitation light, illuminating the test chemical. Additionally or alternatively, the light may be light that is reflected by the test chemical, such as by reflecting and/or scattering primary light. In the latter case, the test chemical may be adapted to change at least one reflective property due to the detection reaction, such as a color.
In the art, many types of test elements including at least one test chemical are known. In many cases, the test elements are in the form of test strips having at least one capillary element for transporting the body fluid from at least one application position, such as from at least one application opening, to one or more test fields including the at least one test chemical.
For example, EP Patent No. 1 482 299 discloses an optical-based test element for use in determining an analyte in a liquid sample. The test element includes a base having a capillary channel formed in a surface of the base, the capillary channel being adapted to move a liquid sample from an inlet to a reaction area formed in the base. The test element further includes a polymer carrier having a lower surface adhered to the surface of the base. The polymer carrier is disposed over at least a portion of the capillary channel. Further, the test element includes a test membrane adhered to the lower surface of the polymer carrier, where the test membrane contains a reagent. The test membrane also extends from the polymer carrier into the reaction area such that the test membrane is arranged to allow the flow of the liquid sample across a bottom surface and an edge of the test membrane.
U.S. Pat. No. 5,759,364 discloses an electrochemical test element that is made up of an insulating base plate bearing an electrode on its surface that reacts with an analyte to produce mobile electrons. The base plate is mated with a lid of a deformable material, which has a concave area surrounded by a flat surface so that when mated to the base plate there is formed a capillary space into which a liquid sample can be drawn. The side of the lid facing the base is coated with a polymeric material that serves to bond the lid to the base plate and to increase the hydrophilic nature of the capillary space.
US Patent Application Publication No. 2007/0278097 discloses a test element including a base substrate on which an electrode system is formed. One or more laminate layers overlie the base substrate to form a sample receiving chamber in which a reagent is deposited. An opening is provided from the sample receiving chamber to the exterior of the test element. The layers and the base substrate are laser welded to secure the test element. One of the layer and base substrate is light-transmissive to allow laser welding at the interface there between. The test element may be formed from a series of continuous webs that are subsequently sliced to form individual test elements.
Int'l Patent Application Publication No. WO 2005/114160 discloses a method of manufacturing a diagnostic test element. Therein, an application sheet is provided, having a plurality of adhesive dots thereon. Further, a first substrate layer is provided having at least one feature located thereon, and, further, a second substrate layer is provided. At least one of the plurality of adhesive dots located on the application sheet is transferred to the first substrate layer, and the first substrate layer is aligned with the second substrate layer and is attached to the second substrate layer, using the transferred adhesive dots. The attaching of the first and second substrate layers is performed without any additional alignment.
Int'l Patent Application Publication No. WO 2004/086970 discloses a method of producing combined puncturing and measuring devices for detecting an analyte in a liquid sample. The combined puncturing and measuring devices include a support and a detection element. Recesses that define puncturing points are formed on a surface of a band-shaped support material. A detection element is applied to the band-shaped support material. Individual puncturing/measuring disposable bodies are separated either singly or in groups from the band-shaped support material at a separating line.
Int'l Patent Application Publication No. WO 99/30158 discloses an analytic test element for determining an analyte in a liquid sample. The test element includes a detection element and a canal that permits capillary liquid transport, where the canal has a test sample feeding opening situated on one end of the canal that permits capillary liquid transport. The canal steadily tapers from the sample feeding opening in a direction of the capillary transport to at least the beginning of the detection element. Herein, the detection element may be inserted in a matching recess integrated into an element that covers the analytic test element.
EP Patent Application Publication No. 1 035 920 discloses a device for collecting liquid samples for analytic test elements in which the liquid sample is transported from a sampling location to a determination location via a capillary active canal. The capillary active canal is essentially produced by a carrier, a covering, and an optional intermediate layer that lies between the covering and the support, whereby a recess is located in an area, the area constructing the canal permitting capillary liquid transport.
Int'l Patent Application Publication No. WO 99/29429 discloses an analytic test element for determining an analyte in a liquid sample. The test element includes an inert carrier, a detection element, and a canal that permits capillary liquid transport. The canal has a liquid sample feeding opening situated on one end of the canal that permits capillary liquid transport and has a vent opening on the other end of the canal. The canal is at least partially constructed by the carrier and the detection element and extends at least to the edge of the detection element, the edge being adjacent to the vent opening, in a direction of the capillary transport.
EP Patent Application Publication No. 1 385 002 discloses a disposable test element having a bonded structure forming channels and a reaction/measurement chamber being positioned over the sensitive surfaces that takes defined liquid sample volumes. As a flat sensor or test strip, the test element has a compartment structure, a sample holding channel with a surfactant on its inner surface or a porous hydrophilic filling and an inflow opening, a reaction/measurement chamber where the mean cross section is at least twice as deep and/or wide as the sample channel, and an enzyme or enzyme system that recognizes the analyte, together with an electron mediator. A sample stop channel with hydrophobic surface coating or a porous filling material has a mean cross section that is at least half as deep and/or wide as the outlet opening from the reaction/measurement chamber. The sample collector zone has a large volume capacity with a mean cross section at least twice as deep and/or wide as the stop channel. The channels and chamber are all interconnected. The structure is irreversibly bonded to the test element so that the reaction/measurement chamber is placed over the sensitive surfaces of the test element.
Despite the advantages implied by the above-mentioned, known devices and methods, a large number of technical challenges remain, specifically regarding designing and manufacturing of test elements, especially optical test elements. Thus, for optical test elements, a uniform test field having a large area and a uniform wetting of the test field is a challenge, as opposed to electrochemical test elements.
Further, manufacturing of capillary elements, specifically at mass manufacturing scale, still is a challenge. This is because a precise positioning of the elements forming the capillary, such as a base foil, a cover foil and spacer elements forming the walls of the capillary, is required. Further, to reduce the liquid sample amount required for a single test, the volume of the capillary has to be reduced. On the other hand, a reliable wetting of the test field and short filling times of the capillary have to be guaranteed. For this purpose, hydrophilic materials such as hydrophilic cover foils are used that are expensive and, thus, contravene the overall desire to keep costs at a low level. Further, by using common processes for manufacturing the test elements, the overall geometry of the capillary structure of the test element imposes tight limits to the design of the test elements, specifically due to the cutting processes that are used for forming the capillaries.
For the foregoing reasons, there is a need for test elements and methods of manufacturing the same that at least partially avoid the above-mentioned problems and challenges of known devices and methods. Specifically, test elements and methods are provided, which, on the one hand, are highly reliable, require small sample volumes and achieve short testing times. Moreover, and on the other hand, manufacturing costs and effort for manufacturing are kept at a low level or even reduced when compared to known manufacturing methods, specifically with regard to a simplification of method steps and positioning steps.